Molecular Relay Research Articles

(Invited) Designing Photocatalytic Membrane to Direct Electron and Hole Transport

Surface interaction of chromophore or redox active molecule which dictate the efficiency of energy/electron transfer, plays an important role in realizing photocatalytic and optoelectronic applications. Metal halide perovskite nanocrystals are interesting in the sense that they can either transfer energy or selectively transfer electrons or holes to the adsorbed molecules.1,2 The presentation will focus on two specific scenarios of the flow of energy and electron processes in CsPbX3 (X= Br, I) nanocrystal-molecular hybrids. The energy transfer is probed through three moleculr acceptors – rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB), which contain an increasing degree of heavy atom pendant groups. Electron and/or hole transfer from excited CsPbX3 nanocrystals to a molecular relay present near the interface offers another avenue to directly convert light energy into chemical energy. Such interfacial electron transfer of semiconductor nanocrystals has been widely explored in photocatalytic processes. A basic understanding of the fundamental differences between the two excited deactivation processes (energy and charge transfer) and ways to modulate them should enable design of more efficient light harvesting assemblies with semiconductor and molecular systems.

Molecular Relays in Nanometer Scale Alumina: Effective Protection Layers for Water-Submersed Halide Perovskite Photocathodes

Halide perovskite (HaP) solar cells have an excellent voltage efficiency (>70%) and a low electron-affinity conduction band minimum, making them prospective candidates to be used as photocathodes in integrated low-cost solar fuel generators. However, halide perovskites are notoriously unstable in aqueous solutions and immediately dissolve upon exposure to liquid water. Ultrathin layers (< 10 nm) of Al2O3 deposited by atomic layer deposition are suitable encapsulants to prevent water ingression but are also electronically insulating. Embedding linear conjugated organic molecules (‘molecular relays’) that transverse the insulating layer enables selective electron transport across the insulating encapsulating layer. The electronic functionality of the embedded molecular relays is verified by conductive probe atomic force microscopy and photo-electrodeposition of metal particles (Pt and Ag) from ethanolic solutions. Lastly, the encapsulated HaP photoelectrodes were submersed in a CO2-saturated aqueous electrolyte and a photocurrent of ~100 µA/cm2 (at ~ -0.32 V vs. Ag/AgCl) was measured. This work demonstrates a way for stabilizing semiconductors in polar and protonic electrolytes as photoelectrodes for the generation of solar fuels.

Molecular Relay Stations in Membrane Nanotubes: IRSp53 Involved in Actin-Based Force Generation.

Membrane nanotubes are cell protrusions that grow to tens of micrometres and functionally connect cells. Actin filaments are semi-flexible polymers, and their polymerisation provides force for the formation and growth of membrane nanotubes. The molecular bases for the provision of appropriate force through such long distances are not yet clear. Actin filament bundles are likely involved in these processes; however, even actin bundles weaken when growing over long distances, and there must be a mechanism for their regeneration along the nanotubes. We investigated the possibility of the formation of periodic molecular relay stations along membrane nanotubes by describing the interactions of actin with full-length IRSp53 protein and its N-terminal I-BAR domain. We concluded that I-BAR is involved in the early phase of the formation of cell projections, while IRSp53 is also important for the elongation of protrusions. Considering that IRSp53 binds to the membrane along the nanotubes and nucleates actin polymerisation, we propose that, in membrane nanotubes, IRSp53 establishes molecular relay stations for actin polymerisation and, as a result, supports the generation of force required for the growth of nanotubes.

Molecular relays in nanometer-scale alumina: effective encapsulation for water-submersed halide perovskite photocathodes.

Halide perovskite (HaP) solar cells have an excellent voltage efficiency (>70%) and a low electron-affinity conduction band minimum, making them prospective candidates to be used as photocathodes in integrated low-cost solar fuel generators. However, halide perovskites are notoriously unstable in aqueous solutions and immediately dissolve upon exposure to water. Ultrathin layers (<10 nm) of Al2O3 deposited by atomic layer deposition are suitable encapsulants to prevent water ingression but are also electronically insulating. Embedding linear conjugated organic molecules ('molecular relays') that transverse the insulating layer enables selective electron transport across the insulating encapsulating layer. The electronic functionality of the embedded molecular relays is verified by conductive probe atomic force microscopy and photoelectrodeposition of metal particles (Pt and Ag) from ethanolic solutions. Lastly, the encapsulated HaP photoelectrodes were submersed in a CO2-saturated aqueous electrolyte and a photocurrent of ∼100 μA cm-2 (at ∼-0.32 V vs. Ag/AgCl) was measured, the highest reported for CsPbBr3 based aqueous photoelectrodes. This work demonstrates a way for stabilizing perovskite semiconductors in polar and protonic electrolytes as photoelectrodes for the generation of solar fuels.

Glycogen synthase kinases in model and crop plants - From negative regulators of brassinosteroid signaling to multifaceted hubs of various signaling pathways and modulators of plant reproduction and yield.

Glycogen synthase kinases, also known as SHAGGY-like Kinases (GSKs/SKs), are highly conserved serine/threonine protein kinases present both in animals and plants. Plant genomes contain multiple homologs of the GSK3 genes which participate in various biological processes. Plant GSKs/SKs, and their best known representative in Arabidopsis thaliana – Brassinosteroid Insentisive2 (BIN2/SK21) in particular, were first identified as components of the brassinosteroid (BR) signaling pathway. As phytohormones, BRs regulate a wide range of physiological processes in plants – from germination, cell division, elongation and differentiation to leaf senescence, and response to environmental stresses. The GSKs/SKs proteins belong to a group of several highly conserved components of the BR signaling which evolved early during evolution of this molecular relay. However, recent reports indicated that the GSKs/SKs proteins are also implicated in signaling pathways of other phytohormones and stress-response processes. As a consequence, the GSKs/SKs proteins became hubs of various signaling pathways and modulators of plant development and reproduction. Thus, it is very important to understand molecular mechanisms regulating activity of the GSKs/SKs proteins, but also to get insights into role of the GSKs/SKs proteins in modulation of stability and activity of various substrate proteins which participate in the numerous signaling pathways. Although elucidation of these aspects is still in progress, this review presents a comprehensive and detailed description of these processes and their implications for regulation of development, stress response, and reproduction of model and crop species. The GSKs/SKs proteins and their activity are modulated through phosphorylation and de-phosphorylation reactions which are regulated by various proteins. Importantly, both phosphorylations and de-phosphorylations may have positive and negative effects on the activity of the GSKs/SKs proteins. Additionally, the activity of the GSKs/SKs proteins is positively regulated by reactive oxygen species, whereas it is negatively regulated through ubiquitylation, deacetylation, and nitric oxide-mediated nitrosylation. On the other hand, the GSKs/SKs proteins interact with proteins representing various signaling pathways, and on the basis of the complicated network of interactions the GSKs/SKs proteins differentially regulate various physiological, developmental, stress response, and yield-related processes.

Proximal-tubule molecular relay from early Protein diaphanous homolog 1 to late Rho-associated protein kinase 1 regulates kidney function in obesity-induced kidney damage

The small GTPase protein RhoA has two effectors, ROCK (Rho-associated protein kinase 1) and mDIA1 (protein diaphanous homolog 1), which cooperate reciprocally. However, temporal regulation of RhoA and its effectors in obesity-induced kidney damage remains unclear. Here, we investigated the role of RhoA activation in the proximal tubules at the early and late stages of obesity-induced kidney damage. In mice, a three-week high-fat-diet induced proximal tubule hypertrophy and damage without increased albuminuria, and RhoA/mDIA1 activation without ROCK activation. Conversely, a 12-week high-fat diet induced proximal tubule hypertrophy, proximal tubule damage, increased albuminuria, and RhoA/ROCK activation without mDIA1 elevation. Proximal tubule hypertrophy resulting from cell cycle arrest accompanied by downregulation of the multifunctional cyclin-dependent kinase inhibitor p27Kip1 was elicited by RhoA activation. Mice overexpressing proximal tubule-specific and dominant-negative RHOA display amelioration of high-fat diet-induced kidney hypertrophy, cell cycle abnormalities, inflammation, and renal impairment. In human proximal tubule cells, mechanical stretch mimicking hypertrophy activated ROCK, which triggered inflammation. In human kidney samples from normal individuals with a body mass index of about 25, proximal tubule cell size correlated with body mass index, proximal tubule cell damages, and mDIA1 expression. Thus, RhoA activation in proximal tubules is critical for the initiation and progression of obesity-induced kidney damage. Hence, the switch in the downstream RhoA effector in proximal tubule represents a transition from normal to pathogenic kidney adaptation and to body weight gain, leading to obesity-induced kidney damage.

The phenomenon of relay race molecular transfer of the amount of motion and its relationship with the diffusion phenomenon

The very fact of molecular transfer of the amount of motion, including in an ideal gas in an equilibrium state, has long been well known. However, this fact is still not realized as a physical phenomenon of transfer, equivalent to such transfer phenomena as diffusion, thermal conductivity and viscosity. The key concept used in this paper when describing the phenomenon of relay race molecular transfer of the amount of motion is the concept - “molecular relay race type of motion”. A molecular relay race model of an ideal gas in an equilibrium state is proposed, as well as a molecular relay race model of a mixture of two ideal gases at constant temperature and pressure. It is shown that the value of the velocity modulus of diffusion flows is one of the physical characteristics of the mixture as a whole. It is also shown that the total density of the substance carried by the diffusion flows is many orders of magnitude less than the total density of the inhomogeneous multicomponent mixture.

A molecular relay race: sequential first-passage events to the terminal reaction centre in a cascade of diffusion controlled processes

We consider a sequential cascade of molecular first-reaction events towards a terminal reaction centre in which each reaction step is controlled by diffusive motion of the particles. The model studied here represents a typical reaction setting encountered in diverse molecular biology systems, in which, e.g. a signal transduction proceeds via a series of consecutive ‘messengers’: the first messenger has to find its respective immobile target site triggering a launch of the second messenger, the second messenger seeks its own target site and provokes a launch of the third messenger and so on, resembling a relay race in human competitions. For such a molecular relay race taking place in infinite one-, two- and three-dimensional systems, we find exact expressions for the probability density function of the time instant of the terminal reaction event, conditioned on preceding successful reaction events on an ordered array of target sites. The obtained expressions pertain to the most general conditions: number of intermediate stages and the corresponding diffusion coefficients, the sizes of the target sites, the distances between them, as well as their reactivities are arbitrary.

Molecular Structural Evolution of Near-Infrared Cationic Aggregation-Induced Emission Luminogens: Preclinical Antimicrobial Pathogens Activities and Tissues Regeneration

Molecular Structural Evolution of Near-Infrared Cationic Aggregation-Induced Emission Luminogens: Preclinical Antimicrobial Pathogens Activities and Tissues Regeneration

Hedgehog Pathway Activation Requires Coreceptor-Catalyzed, Lipid-Dependent Relay of the Sonic Hedgehog Ligand.

Hedgehog signaling governs critical processes in embryogenesis, adult stem cell maintenance, and tumorigenesis. The activating ligand, Sonic hedgehog (SHH), is highly hydrophobic because of dual palmitate and cholesterol modification, and thus, its release from cells requires the secreted SCUBE proteins. We demonstrate that the soluble SCUBE-SHH complex, although highly potent in cellular assays, cannot directly signal through the SHH receptor, Patched1 (PTCH1). Rather, signaling by SCUBE-SHH requires a molecular relay mediated by the coreceptors CDON/BOC and GAS1, which relieves SHH inhibition by SCUBE. CDON/BOC bind both SCUBE and SHH, recruiting the complex to the cell surface. SHH is then handed off, in a dual lipid-dependent manner, to GAS1, and from GAS1 to PTCH1, initiating signaling. These results define an essential step in Hedgehog signaling, whereby coreceptors activate SHH by chaperoning it from a latent extracellular complex to its cell-surface receptor, and point to a broader paradigm of coreceptor function.

Monitoring Embedded Flow Networks Using Graph Fourier Transform Enabled Sparse Molecular Relays

Many embedded networks are difficult to monitor, such as water distribution networks (WDNs). A key challenge is how to use minimum sparse sensors to measure contamination and transmit contamination data to a hub for system analysis. Existing approaches deploy sensors using multi-objective optimisation and transmit the data using ground penetrating waves or fixed-line access. Here, for the first time, we introduce a novel molecular communication relay system, which is able to transmit the data report to the hub via the water-flow of WDN itself, and avoids the complex ground penetrating techniques. A water flow data-driven Graph Fourier Transform (GFT) sampling method is designed to inform the invariant orthogonal locations for deploying the molecular relay sensors. Each sensor encodes information via a DNA molecule that enables the common hub to reconstruct the full contamination information. Numerical simulation validates the proposed system, providing a pathway to integrate MC into macro-scale Digital Twin platforms for infrastructure monitoring.

Tri-functional molecular relay to fabricate size-controlled CoOx nanoparticles and WO3 photoanode for an efficient photoelectrochemical water oxidation

Heterojunction and element doping to couple light-harvesting semiconductors with catalytic materials have been widely employed for photoelectrochemical (PEC) water splitting.

Probing Perovskite Photocatalysis. Interfacial Electron Transfer between CsPbBr3 and Ferrocene Redox Couple.

Interfacial charge transfer between a semiconductor nanocrystal and a molecular relay is an important step in nanomaterial photocatalysis. The ferrocene redox couple (Fc+/Fc0, E0 = -4.9 eV vs vacuum) has now been used as a model redox relay system to investigate photocatalytic properties of CsPbBr3 perovskite nanocrystals. The photocatalytic reduction of ferrocenium (Fc+) to ferrocene (Fc0) with CsPbBr3 nanocrystals was dictated by the surface interactions. Whereas a rapid quenching and subsequent recovery of CsPbBr3 emission is seen at low Fc+ concentrations, the quenched emission was sustained at higher Fc+ concentrations. The photoinduced interfacial electron transfer between CsPbBr3 and ferrocenium (Fc+) studied using transient absorption spectroscopy occurred with a rate constant of 1.64 × 1010 s-1. Better understanding of interfacial processes using redox probes can lead to the improvement in photocatalytic performance of perovskite nanocrystals.

Lobular architecture of human adipose tissue defines the niche and fate of progenitor cells

Human adipose tissue (hAT) is constituted of structural units termed lobules, the organization of which remains to be defined. Here we report that lobules are composed of two extracellular matrix compartments, i.e., septa and stroma, delineating niches of CD45−/CD34+/CD31− progenitor subsets characterized by MSCA1 (ALPL) and CD271 (NGFR) expression. MSCA1+ adipogenic subset is enriched in stroma while septa contains mainly MSCA1−/CD271− and MSCA1−/CD271high progenitors. CD271 marks myofibroblast precursors and NGF ligand activation is a molecular relay of TGFβ-induced myofibroblast conversion. In human subcutaneous (SC) and visceral (VS) AT, the progenitor subset repartition is different, modulated by obesity and in favor of adipocyte and myofibroblast fate, respectively. Lobules exhibit depot-specific architecture with marked fibrous septa containing mesothelial-like progenitor cells in VSAT. Thus, the human AT lobule organization in specific progenitor subset domains defines the fat depot intrinsic capacity to remodel and may contribute to obesity-associated cardiometabolic risks.

Phenoxazine Derivative Operates as an Efficient Surface-Grafted Molecular Relay to Enhance the Performance and Stability of CdS- and CdSe-Sensitized TiO2 Solar Cells.

We report on a new phenoxazine derivative, 10-butyl-phenoxazine-3-carboxylic acid (BPCA), that we designed to operate as a molecular relay in semiconductor-sensitized solar cells (SSCs). After BPCA surface modification and in the presence of a cobalt-bipyridyl complex acting as a redox mediator, both TiO2 /CdS/BPCA and TiO2 /CdSe/BPCA SSCs exhibit enhanced photovoltaic performance and stability. In particular, the power conversion efficiencies of CdS and CdSe-based solar cells are improved by 90 % and 57 %, respectively. Furthermore, after 300 s the JSC of TiO2 /CdS/BPCA SSCs is stabilized at 30 % of its initial value, while in the same time CdS-based devices retain only 1 % of their initial JSC . The origin of the improvement arises from the excellent electron-donating property of BPCA and its role as a powerful molecular relay in non-polysulfide based SSCs.

A Molecular Relay‐Modified CdS‐Sensitized Photoelectrochemical Cell for Overall Water Splitting

AbstractA novel approach to enhance the photocurrent and photostability of semiconductor‐sensitized photoelectrochemical cells (PECs) with a nonsacrificial electrolyte by grafting the CdS surface with a molecular relay, 4‐(N,N‐diphenylamino)benzoic acid (DPABA) is reported. Using this modification, the PECs are able to perform overall water splitting instead of only hydrogen generation. The probable reasons for the improvement are that the photogenerated holes in the CdS valence band could be rapidly removed by DPABA, which facilitates charge separation and thus suppresses the photocorrosion process. The use of such a method might further improve the performance of overall water splitting, together with superior light‐absorption sensitizers and more suitable molecular relays with better oxygen evolution reaction catalytic properties.

Programming A Molecular Relay for Ultrasensitive Biodetection through 129Xe NMR

AbstractA supramolecular strategy for detecting specific proteins in complex media by using hyperpolarized 129Xe NMR is reported. A cucurbit[6]uril (CB[6])‐based molecular relay was programmed for three sequential equilibrium conditions by designing a two‐faced guest (TFG) that initially binds CB[6] and blocks the CB[6]–Xe interaction. The protein analyte recruits the TFG and frees CB[6] for Xe binding. TFGs containing CB[6]‐ and carbonic anhydrase II (CAII)‐binding domains were synthesized in one or two steps. X‐ray crystallography confirmed TFG binding to Zn2+ in the deep CAII active‐site cleft, which precludes simultaneous CB[6] binding. The molecular relay was reprogrammed to detect avidin by using a different TFG. Finally, Xe binding by CB[6] was detected in buffer and in E. coli cultures expressing CAII through ultrasensitive 129Xe NMR spectroscopy.

Programming A Molecular Relay for Ultrasensitive Biodetection through (129)Xe NMR.

A supramolecular strategy for detecting specific proteins in complex media by using hyperpolarized (129) Xe NMR is reported. A cucurbit[6]uril (CB[6])-based molecular relay was programmed for three sequential equilibrium conditions by designing a two-faced guest (TFG) that initially binds CB[6] and blocks the CB[6]-Xe interaction. The protein analyte recruits the TFG and frees CB[6] for Xe binding. TFGs containing CB[6]- and carbonic anhydrase II (CAII)-binding domains were synthesized in one or two steps. X-ray crystallography confirmed TFG binding to Zn(2+) in the deep CAII active-site cleft, which precludes simultaneous CB[6] binding. The molecular relay was reprogrammed to detect avidin by using a different TFG. Finally, Xe binding by CB[6] was detected in buffer and in E. coli cultures expressing CAII through ultrasensitive (129) Xe NMR spectroscopy.

Fast Charge Separation at Semiconductor Sensitizer–Molecular Relay Interface Leads to Significantly Enhanced Solar Cell Performance

We report on an effective strategy to improve the efficiency and stability of liquid junction semiconductor-sensitized solar cells employing cobalt bipyridyl complex-based electrolyte. With CdS-sensitized TiO2 as a model system, we demonstrate that grafting the surface of CdS with small relay molecule, 4′-(bis(4-(hexyloxy)phenyl)amino)biphenyl-4-carboxylic acid (PAPC), drastically improves the cell performance and leads to an unprecedented power conversion efficiency. Transient absorption measurement indicates the photogenerated holes in CdS could be instantaneously intercepted by the grafted PAPC molecules, which greatly facilitates the charge separation and thus stabilizes CdS. We believe such a concept could be applied to other semiconductor sensitizers, especially for those with superior light absorption, such as CdSe, CdTe, etc.

Rictor beyond the TORC: linking the proliferation, migration and FcεRI-mediated degranulation of human mast cells

Rictor is a cytosolic protein that was originally recognized as a specific component of the mammalian target of rapamycin (mTOR) complex 2 (mTORC2). This complex integrates nutrient- and growth factor-induced signaling cascades to regulate cell proliferation and metabolism. An increasing body of evidence however shows that rictor may also function independently of mTORC2 through association with other proteins and complexes. Recent studies on mast cells demonstrated that in the context of mTORC2 rictor positively regulates proliferation of immature and migration of mature mast cells whereas by itself rictor independently functions as a molecular relay that sets the sensitivity of high affinity receptor for IgE (FceRI) for activating mast cell degranulation. These novel findings suggest that rictor is a multifunctional protein that plays a role in synchronization of multiple cellular functions in mast cells.